need troubleshooting help - 1990 f150

[QueBert]

tries to start but doesn't, batteries fine, starter's good. If I spray starter fluid I can get it to start, but it dies after about a second. I thought it had to be the fuel pump, but if what I'm finding on Google's accurate, my truck has a fuel pump on each tank. And it dies the same with either tank selected.

Does my truck have 2 separate fuel pumps? If it does, what else could it be? And if it doesn't, is there anything else it could be?

 

[SearchMaster]

Carburetor, correct? How old is the gas? How long has it been sitting without running? You may have some clogged jets.

 

[QueBert]

I drive it daily, I forgot to mention a few days ago I started it, it ran for about 10 seconds then shut off. it restarted fine and I drove it all day with no issue. and no on the carb it's EFI

 

[dave_the_nerd]

Similar problems. Both fuel pumps conked out, but it wasn't the pump - wiring problem. There's a back-and-forth there; sounds like a few things you can check.

http://www.justanswer.com/ford/4in0m-1990-f-150-5-0-dual-tanks-fuel-pump-issues-over-several.html

 

[QueBert]

thanks for the reply dave, had a mechanic buddy look at it. Wasn't around to watch him, but in about 10 minutes he figured out it was a relay. He unplugged and plugged something in and it's working. UGH I hate cars lol. Wish I had taken shop class in HS and learned how to fix cars.

And thanks for the link, he didnt have time to check that, so I'll pass it along to him to see if that's something I should look into.

 

[mindless1]

in about 10 minutes he figured out it was a relay. He unplugged and plugged something in and it's working. UGH I hate cars lol.

27 years old and only needs 10 minutes and a ~ $12 part... cars aren't so bad these days.

As far as finding the fault, you could have checked whether there was pressure on the fuel rail, there's probably a schrader valve on it. That tells you the pump is working, then you might want to check fuel rail pressure with a gauge, or if no pressure, check fuses and relays, either bad or then check whether power is getting to either fuel pump with a test light or multimeter.

Fuses can be visually checked or with multimeter probes. As far as the relay itself, if you're lucky the fuel pump relay is a part # also used on something else in the vehicle so you can swap the two relays and see if both or either of the subsystems they energize, still work. If it's unique then you can measure 12V getting to it, voltage on the coil when it should be closed circuit, and voltage on the output. Studying a diagram of that relay you can also jumper 12V in to 12V out in the relay socket.